"We need further follow-up and long-term studies," she said, adding, "we are actively evaluating the effect of IVF on breast tissue."

Rancic, the 36-year-old E! and Style Network host, has long documented her struggle to have a baby on her Style Network reality-TV show "Giuliana and Bill," with husband Bill Rancic, the first "Apprentice" winner. Her first round of in vitro fertilization ended in a miscarriage and the second failed to work.

It was during her third round of IVF that her doctor insisted she have a mammogram first, since pregnancy could accelerate the spread of any potential cancer. That's when a tumor was detected.

"Now I truly believe God was looking out for me," Rancic told the "Today" show Monday.

Rancic said her prognosis is good, having caught the cancer at an early stage. "I will be OK, because I found it early," she said.

She will undergo a lumpectomy later this week, followed by six weeks of radiation therapy.

"We are grateful that thanks to early detection, Giuliana is expected to have a swift and complete recovery," E! said in a statement to ABCNews.com, while it applauded her decision to go public with her diagnosis, "in the hope that it will encourage women everywhere to take necessary and preventive measures."

Rancic, who already had embryos retrieved in her latest round of IVF, still plans to pursue pregnancy after her breast cancer treatment.

"I still want this baby," she told "Today." "What's amazing is that baby will have saved my life. If I had gotten pregnant later down the line, I could have been a lot sicker."

Litton doesn't see a problem with Rancic trying to get pregnant.

"Finding cancers early with appropriate detection there are very high cure rates," Litton said. "And it does not take future motherhood off the table."

Dr. Jennifer Mersereau, director of the fertility preservation program at University of North Carolina at Chapel Hill, said that for those who have had breast cancer and wish to become pregnant, studies are "very reassuring that there is not an increased risk of [cancer] recurrence."

As for their chances of conceiving afterward, Mersereau said there is not a whole lot of data. Age at the time of diagnosis, type of treatment and previous fertility history are all factors that can play a role.

Rancic said she was dragged "kicking and screaming" into her mammogram, something she had planned to do at 40. Like 85 percent of all women with breast cancer, she did not have a family history of it.

Rancic shared the following message with women: "A lot of us think we're invincible ... but we have to start putting ourselves on the to-do list. I had a friend call me yesterday, and she said, 'I'm so sorry, can I do anything for you?' And I said, 'Just call your doctor tomorrow and make an appointment. That's what you could do for me.'"

Mersereau said women under 40 shouldn't rush out to get mammograms. Age 40 is still considered the baseline age. But women should tailor their screening depending on many factors, including their family history, Litton said.

"The take home is that this is a really important conversation for women to have to understand their personal risk," Litton said.